稀土冶炼电解槽余热取热试验研究

Experimental investigation on the waste heat recovery from rare earth smelting electrolyzer

冶金行业能耗巨大,稀土冶炼工艺具有同样特点,采用熔盐电解法制备稀土金属时,冶金槽侧壁和冶金槽内熔融液体上表面向外散发出大量热量,并且冶炼过程伴随产生酸性气体。针对稀土冶炼过程中,电解槽以辐射和对流换热的方式向外散失大量余热问题,搭建了稀土冶炼模拟试验槽,采用燃煤放热获得相似的槽内温度场,采用冷却水与模拟电解槽侧壁进行对流换热、与模拟电解槽高温辐射面进行辐射换热,开展稀土冶炼过程中槽壁余热换热和顶部辐射余热换热试验研究。结果表明,槽壁余热换热量随水流量的增大呈上升趋势,水流量对槽壁余热换热量的影响强于辐射受热面与模拟槽顶面距离对其的影响。在试验条件下,模拟槽辐射受热面距离模拟槽顶面0.2 m、水流量为0.285 kg/s时,槽壁余热换热量最大可达2.256 kW。辐射余热换热量受辐射受热面与电解槽顶面距离的影响较大,随辐射受热面与电解槽顶面距离的减小呈增大趋势。辐射受热面与电解槽顶面距离为0.1 m时、水流量为0.292 kg/s时,辐射余热换热量与总余热换热量达到最大值,分别为19.541 kW和21.114 kW。基于试验数据推算的电解槽实际运行工况下辐射余热换热量可达52.796 kW,总余热换热量最大可达83.237 kW,占电解槽总电耗的55.5%,可为研发稀土冶炼工艺的节能减排技术、实现能源的合理利用提供依据。

The energy consumption is very huge in metallurgical industry,and the rare earth smelting process has the same characteristic.When smelting rare earth metals by molten salt electrolysis,a large amounts of heat is released from the side wall and the upper surface of the smelting electrolyzer,producing some acid gas during the smelting process together.In the process of rare earth smelting,a large amount of waste heat is lost in the electrolytic cell by means of radiation and convection heat transfer.A rare earth smelting simulation experimental cell was built,and a similar temperature field in the cell was obtained by using coal-fired heat release.The cooling water was used to conduct convection heat transfer with the side wall of the simulated electrolytic cell and radiation heat transfer with the high temperature radiation surface of the simulated electrolytic cell.The experimental study on heat transfer of tank wall and top radiation in rare earth smelting process was carried out.The results show that the heat transfer rate in the side wall increases with the increase of the mass flow rate of cooling water and the influence of water flow rate on the heat transfer of tank wall is stronger than that of the distance between the radiant heating surface and the top surface of the simulated tank.In the experiments,when the distance between the radiation absorbing surface and the upper surface of the simulated electrolyzer is 0.2 m and the mass flow rate of the cooling water is 0.285 kg/s,the maximum heat transfer rate in the side wall is 2.256 kW.The capacity of the recovered radiation heat is greatly affected by the distance from the radiant absorbing surface and the top of the smelting groove and increases with decreasing the distance.With the distance of 0.1 m and the mass flow rate of 0.292 kg/s,the recovered radiation heat reaches up to 19.541 kW and the total heat transfer rate is 21.114 kW.Based on the experimental data,the practical capacity of the recovered radiation heat and total heat deduced are 52.796 kW and 83.237 kW.The total heat recovered accounts for 55.5%of the total electricity consumption of the smelting process.The above results can be used to supply reference for developing energy saving technology and realizing reasonable utilization in rare earth smelting plant.